LONDON - Police were on standby for street violence after protesters pledged to "celebrate" the death of former British Prime Minister Margaret Thatcher with a party at the scene of a 1990 riot against one of her most unpopular policies.

Senior police officers have already launched an operation to prevent disorder surrounding her televised funeral at St Paul’s Cathedral on Wednesday, which is due to be attended by Britain’s queen and world leaders. Every living former U.S. president is invited.

With tight security around the official event, protest groups have threatened to gather on Saturday in London’s Trafalgar Square, where thousands rioted in March 1990 in protest against the introduction of the Poll Tax – a despised local government tax system that proved to be one of the main triggers of Thatcher’s political downfall in November that year.

Thatcher, the country’s longest serving prime minister in a century and the first woman to hold the job, died on Monday after suffering a stroke at the age of 87.

She is both revered and reviled in Britain, where her free market reforms led a national economic resurgence but also created pockets of deep social deprivation in areas where former state-run industries such as coal mines and steel works were shut down or sold off with the loss of tens of thousands of jobs.

Steve Eason / Hulton Archive via Getty Images, file

Police and demonstrators clash in London's Trafalgar Square during rioting, which arose from a demonstration against the Poll Tax March 31, 1990.

At her own request, she will not have an official state funeral - a decision that appeared to acknowledge that a government-funded event would be controversial and unpopular – and insisted there should be no military fly-past.

However, Wednesday’s ceremony is shaping up to the grandest of its kind since the funeral of wartime leader Winston Churchill in 1964.

Although groups cheering Thatcher’s death are in a minority, police are monitoring social media to gather intelligence on the scale and nature of any protests.

"Some say Margaret Thatcher is a divisive figure, but that's part of the tapestry of policing these events,” Metropolitan Police Commander Christine Jones told the Daily Telegraph. “If people come to London to cause trouble and commit crime we will deal with you.”

Margaret Thatcher, the longest-serving Prime Minister of the United Kingdom of the 20th century and the only woman ever to have held the post, passed away after suffering a stroke. She was 87. NBC's Martin Fletcher looks back at the life and times of the "Iron Lady."

In a statement, she added: “The right to protest is one that must be upheld, however, we will work to do that whilst balancing the rights of those who wish to pay their respects and those who wish to travel about London as usual.”

The force is using its experience from handling the London Olympics in July to deal with the event. Blanket stop-and-search powers are expected to be introduced in the run up to the funeral.

The force also has a Fixated Threat Assessment Centre, which monitors disturbed individuals are obsessed with public figures.

Saturday’s protest is being supported by other groups such as the All London Anarchist Revolutionary Mob, the London Evening Standard reported.

“Miners will be coming down from the north, Wapping printers, steel workers - it will be a big crowd. We are talking thousands,” Class War founder Ian Bone told the newspaper.

“It has been planned for years, always for the first Saturday after her death, and it is in the right place, where the Poll Tax riots were taking place.”

Jones added that dealing with threats of disorder was “part of the normal daily business of London.”

Tributes to Margaret Thatcher have continued, many of them from those closest to her in her final years. They touched on how the former PM was happiest while battling at the eye of the storm in high political office. As one of her closest advisers said, Lady Thatcher never felt truly at home after leaving Number 10 Downing Street. ITN's Tom Bradby reports.

“We deal with more than 3,500 protests or facilitated events a year so this is nothing new,” she added.

Police are also liaising with Britain’s intelligence agencies amid speculation the funeral could be targeted by Irish Republican terrorists – although the overall terror threat level remained unchanged.

Thatcher was targeted by an Irish Republican Army bomb in 1984 in retaliation for her tough stance on the organization, and saw two close political friends killed in terrorist attacks.

Meanwhile, opponents are doing their best to get the "Wizard of Oz" song "Ding Dong the Witch is Dead" to the top of Britain’s version of the Billboard Hot 100. Midweek sales already have it in the Top 5 in the wake of a Facebook campaign.

That means the BBC will have to play the song during its chart show on Sunday. Conservative politicians have called on the broadcaster to not give it airtime.

The BBC says its chart show is a factual account of what the British public has been buying and they will make a decision about whether to play the song when the final chart positions are clear on Sunday.